The present invention relates generally to a lens, and more particularly to a lens module mounted on a circuit board which is provided with a chip for imaging.
As shown in FIG. 1, a lens module 1 of the prior art is mounted on a circuit board 3 which is provided thereon with an electrically-connected chip package 5. The chip package 5 comprises a chip 5a, a chip carrier 5b, and a transparent glass 5c. The chip 5a is disposed in a receiving cell of the chip carrier 5b such that the chip 5a is shielded by the glass 5c. The lens module 1 comprises a seat body 1a, which is fixed on the circuit board 3 by a plurality of screws 1b. The seat body 1a has a threaded hole 1c corresponding in location to the chip 5a. The threaded hole 1c is provided therein with a cylindrical body 1d in which a plurality of lenses 1e are fixed. The image of an object located in the outside of the seat body 1a is formed on the chip 5a via the lenses 1e. The focus between the lens 1e and the chip 5a is adjusted by setting the depth of the cylindrical body 1d in the threaded hole 1c. Such a prior art focus adjustment structure as described is rather inconvenient, complicated in construction, and not cost-effective.
As shown in FIG. 2, another prior art lens module 2 is mounted on a circuit board 4 which is provided thereon with a chip 6 electrically connected therewith. The lens module 2 comprises a seat body 2a which is fastened with the circuit board 4 by a plurality of screws 2b. The seat body 2a has a through hole 2c corresponding to the chip 6. A plurality of lenses 2d are fixed in the through hole 2c. An elastomer 8 is sandwished between the circuit board 4 and the seat body 2a such that the upper end of the elastomer 8 is coupled with the seat body 2a so as to shield the fringe of the chip 6. The elastomer 8 has an elastically expandable pleated portion 8a, which can be caused by an external force to change its height. As a result, the focus adjustment is attained in conjunction with a plurality of screws 2b. In spite of the structural simplicity of the lens module 2, the effect of the components used to adjust or fix the distance between the lens 2d and the chip 6 is by no means simplified or enhanced. The focus adjustment is achieved by adjusting respectively the four screws 2b. In other words, these two prior art lens modules 1 and 2 share a common deficiency.
The primary objective of the present invention is to provide a lens module which is capable of an easy adjustment and fixation of focus between lens and chip.
The lens module of the present invention is mounted on a board body which is provided thereon with an image-forming chip. The lens module comprises a seat body in which at least one lens is fixed for use in enabling an image outside the seat body to impress on the chip. The seat body and the board body are provided therebetween with an expandable tube having a serpentine segment, thereby forming a closed passage between the lens and the chip. The expandable tube is provided with a fixation member serving to limit deformation of the serpentine segment of the expandable tube.